Eastern Tiger Swallowtail

Papilio glaucus

The Eastern Tiger Swallowtail is a species of swallowtail butterfly native to North America. It is one of the most familiar butterflies in the eastern United States, where it is common in many different habitats. It flies from spring to fall, during which it produces two to three broods. Adults feed on the nectar of many species of flowers, mostly from those of the Apocynaceae, Asteraceae, and Fabaceae families. ''P. glaucus'' has a wingspan measuring 7.9 to 14 centimeters . The male is yellow with four black "tiger stripes" on each fore wing. Females may be either yellow or black, making them dimorphic. The yellow morph is similar to the male, but with a conspicuous band of blue spots along the hindwind, while the dark morph is almost completely black.

The green eggs are laid singly on plants of the Magnoliaceae and Rosaceae families. Young caterpillars are brown and white; older ones are green with two black, yellow, and blue eyespots on the thorax. The caterpillar will turn brown prior to pupating. It will reach a length of 5.5 centimeters . The chrysalis varies from a whitish color to dark brown. Hibernation occurs in this stage in locations with cold winter months.

Appearance

The wingspan ranges from 7.9 to 14 cm with females being the larger sex. Southern individuals are larger than northern ones. Males are yellow with four black "tiger stripes" on each fore wing. The outer edge of the fore wing is black with a row of yellow spots. The veins are marked with black. The postmedian area of the hind wing is black with yellow spots along the margin. The inner margin of the hind wing has small red and blue spots. The ventral fore wing margin has a yellow bar that is broken into spots. This broken bar is present in both sexes, and is used to distinguish ''P. glaucus'' from its close relatives.

Females are dimorphic. The yellow morph differs from the male in having a blue postmedian area on the dorsal hind wing. In the dark morph, the areas that are normally yellow are replaced with dark gray or black. The bluish postmedian area on the ventral hind wing has one row of orange spots. A shadow of the "tiger stripes" can be seen on the underside of some dark females.

''P. glaucus'' is one of a few species of papilionids known to produce gynandromorphs. Most bilateral gynandromorphs are hybrids of ''P. glaucus'' and ''P. canadensis'' that are found along hybrid zones. Color mosaics are found in the central part of the species range.

Distribution

''P. glaucus'' is found in the eastern United States from southern Vermont to Florida west to eastern Texas and the Great Plains. It is common throughout its range, although is rarer in southern Florida and absent from the Florida Keys. In 1932, a single specimen was collected in County Wicklow, Ireland. It is believed to have been an accidental introduction from North America. ''P. glaucus'' can be found almost anywhere deciduous forests occur. Common habitats include woodlands, fields, rivers, creeks, roadsides, and gardens. It will stray into urban parks and city yards. Because it has adapted to many different habitats and host plants, ''P. glaucus'' is a generalist, and is not considered threatened.

Adults are seen from spring to fall, although the exact date varies depending on the location. In the south, they are seen from February to November; in the north, they are seen from May to September. ''P. glaucus'' produces two broods in the north and three in the south. The first broods yield the smallest adults.

The Eastern Tiger Swallowtail is the state butterfly of Alabama, Delaware, Georgia, and South Carolina, and is the state insect of Virginia.

Behavior

Eastern Tiger Swallowtails are diurnal, and are usually solitary. Adults are known to fly high above the ground, usually seen above the tree canopy. Males seek females by patrolling habitats containing the larval host plants. During courtship, the male and female fly about each other prior to landing and mating. The male releases perfume-like pheromones during courtship to entice the female into mating.

Adults use a wide range of food sources, most preferring to nectar on sturdy plants with red or pink flowers. Many members of the families Apocynaceae, Asteraceae, and Fabaceae are used as common nectar sources. Males participate in a behavior called puddling, in which they congregate on mud, damp gravel, or puddles. They extract sodium ions and amino acids from these sources which aid in reproduction. Males that puddle are typically fresh, and puddle only for their first couple of days. Females will occasionally puddle, but do not form congregations. Adults have also been seen feeding on dung, carrion, and urine.

Habitat

''P. glaucus'' is found in the eastern United States from southern Vermont to Florida west to eastern Texas and the Great Plains. It is common throughout its range, although is rarer in southern Florida and absent from the Florida Keys. In 1932, a single specimen was collected in County Wicklow, Ireland. It is believed to have been an accidental introduction from North America. ''P. glaucus'' can be found almost anywhere deciduous forests occur. Common habitats include woodlands, fields, rivers, creeks, roadsides, and gardens. It will stray into urban parks and city yards. Because it has adapted to many different habitats and host plants, ''P. glaucus'' is a generalist, and is not considered threatened.

Adults are seen from spring to fall, although the exact date varies depending on the location. In the south, they are seen from February to November; in the north, they are seen from May to September. ''P. glaucus'' produces two broods in the north and three in the south. The first broods yield the smallest adults.

The Eastern Tiger Swallowtail is the state butterfly of Alabama, Delaware, Georgia, and South Carolina, and is the state insect of Virginia.

Predators

The first three instars of the caterpillar are bird dropping mimics, coloration that helps protect it from predators. In later instars, the eyespots on the thorax serve to deter birds. Like all members of the family Papilionidae, the caterpillar of ''P. glaucus'' possesses an osmeterium, an orange, fleshy organ that emits foul-smelling terpenes to repel predators. Normally hidden, the osmeterium is located on the first segment of the thorax, and can be everted when the caterpillar feels threatened. The combination of eyespots and osmeterium makes the caterpillar resemble a snake.

Since adults are palatable, dark morph females use Batesian mimicry to protect themselves from vertebrate predators by mimicking the poisonous Pipevine Swallowtail. Dark morph females are more prevalent in the south, where ''B. philenor'' is more common.

Defense

The first three instars of the caterpillar are bird dropping mimics, coloration that helps protect it from predators. In later instars, the eyespots on the thorax serve to deter birds. Like all members of the family Papilionidae, the caterpillar of ''P. glaucus'' possesses an osmeterium, an orange, fleshy organ that emits foul-smelling terpenes to repel predators. Normally hidden, the osmeterium is located on the first segment of the thorax, and can be everted when the caterpillar feels threatened. The combination of eyespots and osmeterium makes the caterpillar resemble a snake.

Since adults are palatable, dark morph females use Batesian mimicry to protect themselves from vertebrate predators by mimicking the poisonous Pipevine Swallowtail. Dark morph females are more prevalent in the south, where ''B. philenor'' is more common.